1. Technical Field of the Invention
This invention relates generally to wireless communications systems and more particularly to wireless communication devices.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
As is also known, the receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies them. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
As with any integrated circuit (IC), when a radio transceiver is implemented on an integrated circuit, it must include electro-static discharge (ESD) protection circuitry. As is known, ESD protection circuitry includes reverse coupled diodes between inputs of the IC and ground of the IC, between inputs of the IC and a power supply connection of the IC, between outputs of the IC and ground of the IC, and between outputs of the IC and the power supply connection of the IC. The reverse coupled diodes function to route the energy of an ESD event occurring on an input or an output of the IC to ground and/or to the power supply connection of the IC. Further, many ICs include multiple internal ground connections and multiple power supply connections to provide separate grounds and power supplies to circuits of the IC to minimize power supply coupled noise affecting the circuits. For these types of ICs, the ground connections and power supply connections are made external to the IC. However, to provide ESD protection, the grounds are coupled together via diodes as are the power supply connections.
For inputs and outputs of an IC that carry low frequency signals (e.g., in the tens of MHz or below), the parasitic capacitance of the reverse coupled diodes does not significantly affect the signals. However, as the frequency of the signals on the input and/or output of the IC increases, the parasitic capacitance and other parasitic components of the diodes begin to adversely affect the signal (i.e., cause distortion of the signal and/or cause the ground voltages, from circuit to circuit of the IC, to vary). A radio frequency integrated circuit (i.e., a radio transceiver implemented on an IC) includes high frequency input and output connections for transceiving radio frequency signals (e.g., signals having a frequency in the hundreds of MHz to the tens of GHz). Since these inputs and outputs must have ESD protection, the parasitic components of reverse coupled diodes do adversely affect the RF signals.
Therefore, a need exists for electrostatic discharge (ESD) protection of RF input and output connections of a radio frequency integrated circuit that does not adversely affect RF signals transceived via the RF input and output connections.